I don't see anything in that graph that suggests that there's any memory pressure.
I see >1GB of cache. Some stuff is swapped out, true, but I don't see a lot of iowait that would suggest heavy swapping. Sadly we don't have iostat and vmstat, so we don't have any direct measurement.

I see a lo of "exceptions.OSError: [Errno 12] Cannot allocate memory" exceptions in the logs. Let's try with bumping the swap space (which is 512M ATM). IIRC, Python doesn't allow to fork a process if free memory < the current process memory.

Since catlee has fixed the memory usage issue (or at least made it significantly better), what's the action to be taken on this bug? Is the memory usage on this server intended to increase? Do we need to increase the swap? Do we also need to increase the memory even though it's not having any memory issues at the moment?